Perhaps it’s time to stop obsessing over penis size, and start to think more about those underloved lads underneath. A new study has suggested that testicle size plays a role in whether or not a guy is an involved dad, but this is one time less is more: the smaller the family jewels, the better the family man.

Prior research has already suggested that dudes with higher testosterone levels are less into raising kids, but this study, which was published in the Proceedings of the National Academy of Sciences on Monday, is the first to find an independent correlation between testicle volume and parenting. As with other seed-bearing nuts, testicle size determines how much juice is produced, and it seems there’s a kind of law of diminishing returns at work. The greater the semen output in each ejaculation, the smaller the parenting output later on. That matters — a lot.

“We know in modern Western societies children with more involved fathers have better developmental outcomes,” says one of the study’s authors, James Rilling, associate professor of anthropology at Emory University in Atlanta. Rilling and his co-authors wanted to see if they could figure out why some fathers opt out of their kids’ lives — the number of absent fathers, the study notes, increased “precipitously” in the latter half of the 20th century. Was there some biology involved? Testosterone is one factor, but it can vary widely in a guy because of age or diet or general health. “Testicular volume is likely to be a more stable measure than testosterone,” says Rilling.

To test their theory, the anthropologists found 70 biological fathers in Atlanta who were happy to have their brains and their berries measured by an MRI. The brains were monitored while the men looked at photographs of their child. The MRIs showed that the region of the brain most associated with nurturing lit up more robustly in guys with smaller gonads. The study also noted that these men’s brains responded particularly fiercely to pictures of their children displaying some emotion.

In addition, the researchers had the men’s partners fill out questions about how involved their men were in child-care tasks such as taking kids to the doctor and getting up at night to respond to them if they wakened. And true to crude jokes around this issue, fathers who got the thumbs-up from their partners were those with the smaller cojones.

Before women start weighing up potential life partners by what they feel when the men look straight ahead and cough, however, it should be noted that it’s not clear what comes first. Does simply having kids shrink the size of testicles? Unlikely, says Rilling. Nonfathers’ scrota were also put under the MRI, to check that parenting was not the sole determinant of size. “We don’t know the direction of the causality,” he admits. “It could be that as men become more involved in caregiving the testes shrink.” But he believes it’s more likely that guys with a little less in the sack are a little better with the crib.

There’s a branch of evolutionary psychology known as life-history theory, which suggests that since a human’s energy is limited, there is always a competition for resources between mating and parenting. Consider the steep decline in sex that parents of young children often experience because of sheer exhaustion. Life-history theory suggests a similar type of equation happens on a specieswide scale: energy either goes to raising the young or making more young ones. “Collectively, these data provide the most direct support to date that the biology of human males reflects a trade-off between mating and parenting effort,” claims the study.

While this is unlikely to herald a change in the way women seek mates, we may be at the beginning of an era when being called ballsy is no longer just a compliment.

@vikingrxcom I also read that longer penises are better for fertility. If you are having issues with erectile dysfunction or need Herbal Viagra try out some alternatives with out side effects. stick to the natural stuff.

This tone of breezy disregard of men is such a sad and telling affectation. It was fresh -- as a gimmick -- in an episode or two of Maude, but that was 1974. And this stands in such stark contrast with the reverential tone your ilk use in all public
discussions of things feminine. So your double standard about the sexes reveals so much that is questionable about you that I feel kind of dirty for looking. What I read is a poor soul just aping the jaded, world-weary attitudes of those sophisticated thought leaders who have gone before her --- well, at least as seen in storylines from Sex in the City. And such lame euphemisms for genitals don't come off right when a girl/woman uses them. It's like hearing your saintly grandmother curse. Sweetheart, here's an insight you can't learn from the squat-to-pee beta males you may know from your local gastropub: the kind of men to whom you might really be sexually attracted (at least in your unguarded, honest moments) don't use those terms. Your use of this language just tells a tale of cringing sexual insecurity around men,
leavened by deep bitterness and resentment bred of rejection, inadequacy and a loudly ticking biological clock.

Women already choose guys with smaller testicles as husbands and fathers, they're called Beta males. A short definition would be: Beta males trade resources for affection. Alpha males trade affection for resources. Quite a few evolutionary psychologists have pointed out that young women tend to have intense sexual relationships with Alphas, then when they are ready to settle down they choose a Beta with the best chance of providing resources for their offspring over X number of years. Not all women follow this path but the majority do.

I just read that men with smaller testicles are MORE FERTILE. So there goes your theory about testosterone. People, don't listen to this demeaning stuff about your testicles. Be the best person you can be. I've listened to stupid articles about people, men, women and their childbearing issues for decades. It leads to terrible situations. Don't listen to Time magazine especially. It's a bunch of sensationalist whoohah.

As a physician who has done many physicals on men, I would say that the size of the testicle is coincidental to this issue, but a belief in Scripture that we should teach our kids is HUGE, Deuteronomy 6:7. Why don't they check the color of hair or how many teeth--so much craziness.

Gorillas apparently have smaller balls, are happy to have less sex (only a few times a year!), are faithful to a few partners and make better dads.Bonobo's have larger balls, have lots of sex with multiple partners and make much poorer dads.

It makes evolutionary sense that if you have less sex, less partners and make less babies, that you would also need to look after your genetic offspring better. That's how the genetic small ball gene lives on and prospers, it's linked to a likelihood of being a good dad and faithful partner (perhaps).

Ms. Luscombe's reporting in this story illustrates a marked asymmetry in reporting that involves discussion of sexualized parts of men and women. From the title to the last clause, men's testicles are referred to in slang, sometimes junior-high-school terms: "'nads", "family jewels," "berries," "cajones," -- not to mention the reference to "seed-bearing nuts" and "juice." (Though it might be worth noting that most of the "juice" is the product of the prostate, not the testes.)

I'm not playing the "offense card" here. It would probably be better if we all loosened up about these things. But, I'm willing to bet at pretty long odds that , if research correlated female breast size with maternal behavior, Time.com would *not* have published an article that included terms like, "mellons," "titties," "casabas," "headlights," "rack," "boobies," and so forth. If I'm right about that, why is that true? Why is it that the only acceptable words for reporting about female anatomy are clinical words and anything goes when reporting about men's anatomy? I'd be particularly interested in Ms. Luscombe's thoughts on that.

So, in other words, TIME Magazine decided to write an article about a study that was published only 2 days ago, and treat it like it's Gospel.

What's funny is that the study only revealed correlation - not causation - between 'ball size and parenting.' That's about as significant as saying that, "a correlation exists between cloudy days and a high chance of rain." In other words, just because it's cloudy does not mean that rain will automatically fall. Wow, big whoop.

What's even funnier is that the study only surveyed 70 men, and based its conclusions on that small of a sample.

What's funniest is that TIME did not give it time (pun intended) for other scientists to 1) examine the findings, and then 2) attempt to replicate the findings - thereby corroborating the results of the study. Instead, this article was published as a 'shock feature' to attract readers to the page.

i have my doubts about this study. My former wife would still say I was the primary care giver and most loving nurturer in our family (so would my daughter). I only wish mine were of a smaller dimension, they are always in the way and annoy me greatly to say the least.

@Kafir Liberals and conservatives share the blame for promoting fatherlessness in poor, disproportionately minority, families. The liberals wanted to provide a "safety net" for these families and the conservatives went along with it only if we included a "no man in the house" rule. (Seriously, social workers would look for signs that there was a man living in the house--men's clothes and such--and the family could lose their welfare benefits if they determined that a man was living there.) Conservatives could muster up enough sympathy for "women and children" *if they were on their own* but not if there was a man around. That meant that, for many poor families, it was economically advantageous for the woman to be raising the children alone. Then the draconian child support system was devised with liberals focused on improving support for poor "women and children" and conservatives willing to accept that as long as the money was coming from the "shiftless men."

It would have been far better if we'd adopted policies that promoted families staying together and providing job training to both moms and dads. That would still be much better now. But we're not going that way.

@dhubin My guess is that it's because, for whatever reason, most guys don't mind using slang to describe their goods, while too many gals do. And Time is smart enough not to intentionally irritate their readers. Now, why do ladies get upset by the word "boobies" or "rack"? Got me -- and I'm a girl! But some do, so it makes sense for Time to avoid the issue.

Also, news sites do this all the time. When a study has a results slghtly leaning in one direction that will get their page more views they jump all over it. This is no medical journal and it does not claim to be.

@dhubin@Kafir Agreed. Both parties are to blame for the fiscal mess we're in. Funny how when government tries to help people, they end up hurting more often than not. Now, they're going to help us with health care.

Yes, I understand that clouds are related to rain. However, a cloudy day does not automatically mean that it will rain.

What the study in the article found was that ball size was related to 'parenting.' However, larger or smaller balls do not automatically mean one thing or another.

In both instances, the "catalysts" (i.e. balls/clouds) do not necessarily cause the effects to occur. They may be related, but not enough to claim that one causes the other. Therefore, as you mentioned, it's rather silly to hype studies like that which really don't say much at all.

It's indeed hype-worthy, but ultimately not fulfilling once you dig a little deeper.